Initialize view

*.kt

//Sample 1
private var button: Button = findViewById(R.id.button)

//Sample 2
private var button: Button? = null
private fun init(){ button = findViewById(R.id.button) }

//Sample 3 (The lateinit keyword stands for late initialization. lateinit modifier is allowed only on mutable properties)
private lateinit var button:Button
private fun init(){ button = findViewById(R.id.button) }

//Sample 4
private val button:Button by lazy { 
  findViewById(R.id.button) as Button
  // or
  findViewById<Button>(R.id.button)
}
// we need use to init button
button.setOnClickListener{  }

//Sample 5 (use view id directly)
button.setOnClickListener {textView.text = "Hello Kotlin"}

//Sample 6
var textView: TextView? = null
textView = findViewById(R.id.textView)
textView?.text = "Sample Text"